The present invention relates to a thin-film magnetic head and a method for fabricating the same.
According to a current method as described in Japanese Provisional patent specification No. 57-58216, a thin-film magnetic head is fabricated by forming a lower coil section on a flat surface of an insulating substrate and depositing a first, thin layer of resin on the coil section. Permalloy is deposited on the first resin layer, forming a lower core half on which a gap-defining insulating layer is formed. An upper coil section is then formed in a second resin layer which is deposited on the gap-defining layer. Finally, an upper core half is formed on the second resin layer. Because of the small thickness the first resin layer follows the contours of the lower coil section and as a result the overlying lower core half follows an undulating contour of the first resin layer. Since this undulating configuration results in a poor operating characteristic, the prior art method is found to be unsatisfactory.
According to one approach, a lower coil section is formed in a groove of a ferrite substrate by depositing copper or aluminum followed by the deposition of fused glass typically at a temperature in the range between 450.degree. C. and 750.degree. C. on the coil section. The substrate is then lapped to remove an excess amount of the fused glass until it presents a common flat surface. An upper coil section is formed on the glass-filled portion, followed by the successive deposition of a gap-defining layer and a ferrite core layer thereon.
While this approaches eliminates the undulation problem, the high fusion temperature of the filling glass tends to oxidize the underlying conductor. Since the conductor has a different coefficient of thermal expansion than the substrate, the heat produced by the fused glass could lead to a serious damage in the core structure. A further disadvantage is that, since the lower coil section is to be formed on the bottom of a groove, difficulty is encountered in uniformly applying a photoresist layer, and since a photomask must be placed on the surface of the substrate, the light passing through it tends to be defocused on the bottom of the groove, producing a blurred image. This imposes limitations on the number of coil turns which can be fabricated.